The invention relates to the technical field of medicines and provides a metformin hydrochloride medicine composition as well as a preparation method and application thereof. The metformin hydrochloride medicine composition comprises the following components in parts by weight: 100-150 parts of metformin hydrochloride, 5-10 parts of pregelatinized starch, 5-10 parts of mannitol and 1-5 parts of magnesium stearate. The preparation method comprises the following steps: uniformly mixing the metformin hydrochloride, the pregelatinized starch and the mannitol, adding water to pelletize, further adding the magnesium stearate, and uniformly mixing, thereby obtaining capsules or tablets. According to the embodiment of the invention, contents of the metformin hydrochloride, the pregelatinized starch and the mannitol are limited, medicines are slowly released in bodies, direct irritation of the metformin hydrochloride to gastrointestinal tracts can be alleviated, side effects, particularly serious gastrointestinal tract reactions, can be reduced, an effective blood concentration can be maintained, the compliance and the security of medicine taking can be improved for patients, the patients can tolerate the composition, and long-term treatment can be facilitated.